It is known to prepare a replaceable refill assembly incorporating a fluid reservoir by filling the reservoir with fluid to be dispensed, applying a valve assembly across the only outlet from the reservoir and then evacuating air or other gases from the reservoir by applying a vacuum across the valve assembly. Once all of the air is evacuated from the reservoir, the refill assembly incorporating the reservoir and its valve assembly is ready for coupling in a dispensing apparatus. The refill assembly has the advantage that it is ready to use in dispensing of the fluid without the need to evacuate further air or other gas from the reservoir. The valve mechanism attached to the outlet of the reservoir typically includes a one-way valve permitting air to be drawn outwardly from the reservoir, however, preventing air or other materials to flow into the reservoir. Advantageously, the one-way valve permits air or other gas to be drawn outwardly from the reservoir under a first vacuum pressure below atmospheric, however, an increased second vacuum pressure farther below atmospheric pressure, is required to draw the fluid outwardly pass the one-way valve. By selecting an evacuating vacuum which is between the first vacuum pressure but not as great as the second vacuum pressure, all of the air may be drawn out and once the air is drawn out, the fluid to be dispensed is not drawn out since the evacuating vacuum while adequate to draw out the air is not adequate to draw out the fluid.
The applicant has appreciated a difficulty which can arise when under certain circumstances, the vacuum which is required to draw air from the reservoir is approximately the same as or is less than the vacuum required to draw fluid from the reservoir. For example, under some circumstances, a one-way valve may be desired to have a sufficient inherent resiliency against opening that the vacuum necessary to be applied to draw air out is substantially equal to the vacuum required to draw fluid out. For example in some circumstances, a very strong bias against opening of the one-way valve may be desired when the fluid to be dispensed is a very low viscosity such as alcohol. In other circumstances, the resistance of the one-way valve to flow outwardly therepast may be desired to be very high as, for example, when the material may comprise viscous fluids or pastes such as soaps with granular particles such as pumice and a strong inherent bias of the valve member to move to a closed position is necessary to create a proper seal on normal closing of the valve member.